Conventionally, a plasma etching method for performing a process on a substrate to be processed such as a semiconductor wafer and an LCD substrate by using a plasma is widely employed. For example, in a manufacturing process of a semiconductor device, a plasma etching process for plasma etching a thin film and the like formed on a semiconductor wafer to thereby remove them is widely used in order to form a fine electric circuit on a substrate to be processed, e.g., a semiconductor wafer.
In an etching apparatus for performing such a plasma etching process, a plasma is generated in a processing chamber (an etching chamber) configured to be airtightly sealed. Further, a semiconductor wafer is mounted on a susceptor disposed in the etching chamber and an etching is carried out thereon.
Further, there are various types of units for generating such a plasma. For instance, in an apparatus for generating a plasma by supplying a high frequency power to a pair of parallel plate electrodes disposed in parallel to face each other vertically, one of the parallel plate electrodes, e.g., a lower electrode, serves as a susceptor. Further, a semiconductor wafer is disposed on the lower electrode and a high frequency voltage is applied between the parallel plate electrodes, whereby a plasma is generated and an etching is carried out.
However, in such an etching apparatus, there may occur a so-called surface arcing that causes a thunder-like abnormal discharge on a surface of a semiconductor wafer during an etching.
The surface arcing possibly occurs, for example, when an insulating layer formed on a conductive layer is etched. For example, in case when an insulating layer formed of a silicon oxide film is etched to form a contact hole leading to a lower conductive layer formed of, e.g., a metal layer, the silicon oxide film whose thickness is reduced by etching may be destroyed due to the surface arcing.
Further, when the surface arcing occurs, a large portion of the silicon oxide film of the semiconductor wafer is destroyed, so that most devices of the semiconductor wafer will become faulty. Furthermore, metal becomes contaminated in the etching chamber, whereby the etching process cannot be continued under such a condition and it is necessary to clean the inside of the etching chamber. Accordingly, the productivity gets significantly lowered.